Study design: This is an open retrospective monocentric cohort study including septic critically ill patients from november 2008 to january 2010. To determine the incidence and the specific risk of nephrotoxicity of aminoglycosides, only hospitalized patients without initial acute kidney injury or with rapidly improving kidney function during the three first days will be included.Primary outcome will be the occurrence of acute kidney injury assessed with the RIFLE classification (Risk, Injury, Failure, Loss, and End-stage kidney disease) from day 4 to day 15. Patients receiving aminoglycosides will be compared with a control group, i.e. not receiving them. We estimated hazard ratios (HR) and 95% confidence intervals (CI) with adjusted and propensity score (PS)-matched Cox-proportional hazards models.